Background: A definite correlation between the distinct genetic variability present in Blastocystis hominis parasite and its pathogenecity has not yet been confirmed.

Objectives and Methods: The first objective of this study was identify the genotypes of B. hominis clinical isolates obtained from 28 gastrointestinal symptomatic patients and 16 asymptomatic individuals by PCR using sequenced-tagged site (STS) primers. The second objective was evaluation the pathophysiological variability between different B. hominis genotypes induced in experimentally infected rats by identify the histopathological changes, the mortality rate and the intestinal cell permeability in Ussing chamber. Infected rats with asymptomatic and symptomatic human isolates were used.

Results: Only 4 B. hominis genotypes were identified among all the human clinical isolates. Subtypes 1, 2, 3 and 4 were detected among 18.2%, 9.1%, 54.5% and 18.2% of the human isolates. In symptomatic isolates subtypes 1, 3 and 4 were detected in 28.6%, 57.1% and 14.3% respectively. In asymptomatic isolates subtypes 2, 3 and 4 were identified in 25%, 50%, and 25% respectively. Subtype 3 was the commonest among humans. Different degrees of pathological changes were found among infected rats by symptomatic subtypes as compared with asymptomatic subtypes. The moderate and severe degrees of pathological changes were found only in symptomatic subtypes infected rats while mild degree was found only in asymptomatic subtypes infected rats. No extra intestinal lesions were found. Only subtype1 induced mortality rate with 25% among infected rats. On evaluation of the intestinal cell permeability, a prominent increasing in short circuit current (ÄIsc) was found in symptomatic subtypes 1 compared to symptomatic subtypes 3 and 4 infected rats. Meanwhile, minimal effects were found in asymptomatic and control groups.

Conclusions: Subtype 1 is relevant to the pathogenecity of B. hominis while, subtype 2 is irrelevant. The presence of subtypes 3 and 4 among symptomatic and asymptomatic isolates suggested that the variability on Blastocystis pathogenecity among these subtypes may be related to the presence of sub-strains (pathogenic or non-pathogenic) which needs further studies.

Session Details

Date:

19/04/2008

Time:

00:00-00:00

Session name:

18th European Congress of Clinical Microbiology and Infectious Diseases